"Quantitative easing" refers to steps that the U.S. Federal Reserve takes in attempting to boost the country's lagging economy. Historically, the Fed's main tool for spurring growth has been lowering short-term rates. However, QE employs expansionary monetary policy, which involves the purchasing of bonds when the interest rate can no longer be lowered. In September of 2012, the Fed announced its third round of quantitative easing, often abbreviated to "QE3." The bank began buying mortgage-backed securities and Treasury bonds in late 2008 to curb mortgage rates and jumpstart the housing market.